Operating instructions

TRACe Subsystem R&S ESCI
1166.6004.12 6.226 E-1
The block diagram below shows the analyzer hardware from the IF section to the processor. The IF filter
is the resolution filter of the spectrum analyzer with bandwidths selectable from 300 kHz to 10 MHz. The
A/D converter samples the IF signal (20.4 MHz) at a rate of 32 MHz.
The digital signal is down-converted to the complex baseband, lowpass-filtered, and the sampling rate is
reduced, i.e. the output sampling rate is set between 15.625 kHz and 32 MHz by dividing the original
sampling rate by powers of 2. This avoids unnecessary oversampling at narrower bandwidths, which
saves processing time and increases the maximum recording time.
The I/Q data are written to separate memories of 128 k words each (512 k words with option R&S
FSP-B70). The memories are hardware-triggered.
I Memory
128 k
Processor
Analog
IF filter
Bandwidths
300 kHz
1 MHz
3 MHz
10 MHz
Analyzer IF
20.4 MHz
A
D
A/D
converter
32 MHz
sampling
clock
Digital down conversion
+ decimation
cos
sin
decimation
filters
NCO
20.4 MHz
Q Memory
128 k
sampling rate
32 MHz / 2
n
n = 0 ... 11
Data aquisition hardware
I data
Q data
Trigger
Fig. 6-1 Block diagram illustrating signal processing in analyzer
TRACe<1|2>:IQ:AVERage[:STATe] ON|OFF
The command enables averaging of the recorded I/Q data provided that I/Q data acquisition was
previously enabled with TRAC:IQ ON and the sampling rate was set to 32 MHz.
Note: Averaging is not supported at sampling rates <> 32 MHz or for a trigger offset < 0.
Example: TRAC:IQ ON 'Switches on acquisition of I/Q data.
TRAC:IQ:SYNC ON 'Switches on synchronization of the aquision of I/Q
'measurement data with the trigger time.
TRAC:IQ:SET NORM,10MHz,32MHz,EXT,POS,0,2048
'Reads 2048 I/Q values starting at
'the time of trigger.
'Filter type: NORMAL (analogue)
'RBW: 10 MHz
'Sample Rate: 32 MHz
'Trigger: external
'Slope: positive
TRAC:IQ:AVER ON 'Enables averaging of the I/Q measurement data.
TRAC:IQ:AVER:COUN 10 'Selects averaging over 10 data sets..
TRAC:IQ:DATA? ''Starts the measurement and reads out the averaged
'data.
Characteristics: *RST value: OFF
SCPI: device-specific
Mode: A-Z